(pronounced: "Gertite") named after the German polymath Johann Wolfgang von Goethe, is an
iron bearing oxide mineral found in soil and other low-temperature
Goethite has been well known since prehistoric
times for its use as a pigment
. Evidence has been
found of its use in paint pigment samples taken from the caves of Lascaux in France.
first described in 1806 for occurrences in the Mesabi iron ore district of Minnesota.
Recently, nanoparticulate authigenic
goethite was shown to be the most
iron oxyhydroxide in
both marine and lake sediments.
It is an iron
. Goethite's hardness ranges from 5.0 to 5.5 on the
, and its
varies from 3.3 to
4.3. The mineral forms prismatic needle-like crystals
, but is more typically massive.
are both polymorphs of the iron
oxyhydroxide FeO(OH). Although they have the same chemical formula
as goethite they each have different crystalline structures making
them distinct minerals.
Its main modern use is as an iron ore
being referred to as brown iron ore
. It does have some use
as a clay earth pigment
soils developed over
rocks in tropical climates
are mined for their iron content as well as other metals.
Goethite often forms through the weathering
of other iron-rich minerals, and thus
is a common component of soils
. It may also be
precipitated by groundwater
or in other
sedimentary conditions, or form as a primary mineral in hydrothermal
Goethite is found all over the planet, usually in the form of
(a form consisting of tiny round grains
cemented together), reniform (kidney shapes) or botryoidal
(globular, like bunches of grapes) accumulations. It is frequently
encountered in the swampy areas at the head of spring waters
'), on cave floors, and on the
bottom of lakes and small creeks. The boxworks
resulting from the oxidation
of sulfide ore deposits is formed of
goethite along with other iron oxides and quartz.
Significant deposits of goethite are found in
England, Australia, Cuba, and
Michigan, Minnesota, Missouri, Colorado, Alabama, Georgia, Virginia, and Tennessee in the United States.
significant in location, if not in abundance, have been found in
Gusev by NASA's Spirit rover,
providing strong evidence for the presence of liquid water on the
planet Mars in an earlier stage of its